The present invention generally relates to industrial robots having sensor units, and more particularly to an industrial robot which comprises a nozzle for spraying a liquid and a sensor for detecting a position, and is designed so that mist, droplet, and the like in the sprayed liquid do not adhere onto the sensor which is located in the vicinity of the nozzle.
When coating paint on the inside of a box-shaped object such as a locker which has a door with a window, it is desirable to automatically and efficiently carry out the painting operation. Thus, instead of the conventional method of painting which relies on manual operation, it is conceivable to employ an industrial robot carries out the painting operation during a manufacturing process of the box-shaped object. However, if the door is already assembled onto the object during the manufacturing process before the painting process, it becomes necessary to open the door in order to paint the inside of the box-shaped object.
Hence, if an attempt is made to automate the above process by the conventional means, an independent robot must be provided in addition to the painting robot so as to open the door before the painting operation is started. However, when a playback type robot which must be taught the operations to be carried out, is used as the robot which opens the door, the door to be opened must always be located at a predetermined closed position. In this case, a stopper must be mounted on the door to keep the door in the predetermined closed position before the painting process, and the mounted stopper must be removed after the painting process, but such operations are troublesome to carry out.
Accordingly, the present inventors have developed an industrial robot which opens the door and paints the inside of the box-shaped object. This developed robot comprises a nozzle for spraying paint at a tip end of an arm, and a sensor and a engaging member respectively provided in the vicinity of the nozzle. The sensor of the robot detects the location of the door, and the engaging member engages with the door to open the door in response to the detection made by the sensor. After the door is opened, the inside of the box-shaped object is coated with the paint which is sprayed from the nozzle. According to this developed robot, the operation in which the door is opened and the operation in which the box-shaped object is painted are both carried out by the same robot, and it is unnecessary to provide an independent robot exclusively for opening the door. In addition, because the location of the door is detected by the sensor, it is possible to positively detect and open the door regardless of the location of the door on the box-shaped object which is conveyed from a preceding process by a belt conveyer.
However, the sensor of the above robot is provided in the vicinity of the nozzle. Therefore, there was a problem in that the sprayed paint easily adhered onto the sensor during the painting operation. When the sprayed paint adhered onto the sensor, the detecting function of the sensor deteriorates, and in extreme cases, the the sensor became incapable of carrying out the detection. The present inventors have thus designed the robot so that the sprayed paint and the like do not adhere onto the sensor.